The invention relates to a method of plastically deforming a hub bore of a fast-running turbine component.
From European Patent Document EP 086 505 A1, a method is known which is used for preventing an expansion of the hub bore of a part, which expansion is caused during an overspeed test of turbine parts as a result of a plastic flowing of the material of the turbine part in the area of the hub, in that the hub bore is plastically deformed prior to the overspeed test. Here, the plastic deformation takes place mechanically by means of a drawing mandrel, a pressing mandrel or a roller and leads to an expansion of the hub bore, which results in a state of tension of the material in the area of the hub bore which virtually anticipates the stressing during the overspeed test.
From German Patent Document DE 43 37 517 A1, a method for the internal high-pressure metal forming of hollow offset shafts made of a cold-formable material is known; during which a tube-shaped starting material, in a tool with an inner contour corresponding to the desired final outer shape of the shaft, is expanded by means of a fluid, which may be a gas or a liquid; by applying a still higher sizing pressure, the expanded workpiece is then sized to the inner contour of the tool; and finally, while maintaining the sizing pressure, is then upset in the longitudinal direction to its final shape. In the case of this known method, a plastic deformation therefore takes place of a relatively thin-walled material to a final outer contour which is significantly different from the original contour of the tube-shaped starting material, in order to produce, for example, drive shafts of a motor vehicle which have a larger outside diameter with a thinner wall thickness in a central tube area and have a smaller outside diameter and a thicker wall thickness at end areas constructed on both sides. In particular, differences in wall thicknesses are to be achieved in the case of such shafts which many times exceed former process limits known in such internal high-pressure metal forming.
Furthermore, a hollow shaft is known from European Patent Document EP 0 509 238 A1 on which parts are fastened by hydraulic expansion. These parts have a central bore whose diameter is slightly larger in the starting condition than the outside diameter of the hollow shaft, so that the parts can be brought into the desired position on the hollow shaft before the hydraulic expansion operation takes place. As a result of the hydraulic expansion of the hollow. shaft, restoring forces are generated which result in a force-locking connection between the fitted-on parts and the hollow shaft.
Finally, from German Patent Document DE 213 421, a process is known for removing machine components disposed on axles or shafts, for example, for pulling off belt pulleys or rope pulleys, flywheels, turbine wheels or the like from their axles, during which a suitable liquid is pressed at a very high pressure on the interior surface of the hub disposed on the shaft. The pressure liquid fed by way of a bore provided in the hub seeks to expand the hub and press it away from the shaft, simultaneously the liquid subjected to a high pressure penetrating into the fitting surfaces between the hub and the shaft, and as a result, having the purpose of facilitating the removal of the machine component to be detached.
It is an object of the invention to increase the ceiling speed of a fast-running turbine component.
This object is achieved in that the plastic deformation of the hub bore takes place by hydraulic expansion by way of a hydraulic fluid fed at a high pressure into the hub bore of the turbine component.
Advantageous further developments of the invention are characterized in the subclaims.
By way of the invention, a method is provided for increasing the ceiling speed of a fast-running turbine component, in the case of which the hub bore of the turbine component is subjected to a plastic deformation. According to the invention, it is provided that the plastic deformation of the hub bore takes place by a hydraulic expansion by way of a hydraulic fluid fed at high pressure into the hub bore of the turbine component.
Preferably, it is provided that the hydraulic expansion of the hub bore takes place by way of a hydraulic device inserted into the latter, which makes it possible that a recess provided between the hub bore and the hydraulic device and sealed off toward the outside by sealing devices can be acted upon under pressure by the hydraulic fluid.
According to an embodiment, it may be provided that the sealing devices act in the radial direction between the hydraulic device and the hub bore.
According to another embodiment, it may be provided that the sealing devices act in the axial direction between the hydraulic device and the hub bore.
It is particularly advantageous to further develop the method according to the invention such that the hydraulic expansion of the hub bore takes place during a balancing step in the production of the turbine component, during which the turbine component is mounted on a balancing mandrel constructed as a hydraulic device.
The method according to the invention is particularly suitable when the turbine component is a compressor impeller of a turbine.
In the case of a turbine component produced from a forged unmachined part, the hydraulic expansion of the hub bore can take place before or after the milling of the blade channels.
In the following, an embodiment of the invention will be explained by the drawings.